Delays in delivering a complete cycle network across London are preventing the streets from being safe for cyclists, claims the London Assembly.
The London Cycle Network Plus is expected to cost about £140m
The London Cycle Network Plus, a network of radial and orbital routes covering the whole of London, is due to be completed in 2009/10.
The Assembly says delays caused by funding problems are preventing more Londoners from taking up cycling.
But Transport for London (TfL) said the number of cyclists in London has risen.
London Assembly's Darren Johnson said: "An increasing number of Londoners are interested in cycling but they need to be accommodated with safe and suitable spaces to ride.
"The London Cycle Network Plus should have a positive impact on cycling and could drastically reduce accident hotspots."
The Assembly says the comprehensive cycle network for London could increase the number of kilometres cycled in the capital by up to 300%.
But TfL said around 400kms of London Cycle Network Plus has already been completed and the network is well on target to be completed by 2009/10.
"The London Cycle Network Plus is having a positive impact on the level of cycling in the capital with a well designed cycle network," a TfL spokesman said.
"Transport for London is investing record amounts in the capital's cycle network and we remain fully committed to working with the London Boroughs and cycling groups to complete the network on time."
He said the number of cyclists in London has risen by 40% during the past five years.
The overall cost of the project is expected to be about £140m.
The London Assembly begins an investigation to review the progress of the LCN Plus on Monday.